1. Field of the Invention
The present invention relates to improvements in bearing apparatus for gear type power transmission systems which comprises a gear casing or housing containing therein a lubricating oil for gears and the like, gearing for a power transmission retained in the casing and a bearing positioned in the casing for rotatably supporting the gear shaft, the bearing being a ball bearing, conical roller bearing, cylindrical roller bearing, needle bearing or spherical bearing.
2. Description of the Prior Art
A known bearing hitherto used in the above mentioned type of bearing apparatus is of open type in which no sealing element is provided and the lubrication of the bearing is effected by way of immersion lubrication or splash lubrication. For immersion lubrication, the bearing is immersed in oil retained in the gear casing. For splash lubrication, the bearing receives lubricating oil splashed by the gears as the gear shaft rotates.
In this kind of gear type power transmission system such as a transmission and reduction gear system, there are problems of wear of the bearing. As well known in the art, fine particles, resulting from the abrasion between the gears and the wear at other parts and due to lapping compound falling off the gear teeth where the lapping compound has adhered at the time of gear finishing, often penetrate into the lubricating oil retained in the gear casing as foreign matter. After being mixed with the lubricating oil, such contaminant foreign particles enter the interior of the bearing together with the oil and causes wearing of the bearing and early flaking thereof. Thereby, the effective life of the bearing is substantially shortened. This kind of trouble is most evident in bearings used in automobile transmissions. The foreign particles bite into the race surface of the bearing to form indentations thereon. From these indentations, cracks are developed which lead to an early flaking of the bearing. This type of bearing breaking or so-called surface originated flaking has been ascertained in various experiments.
Also, for final reduction gear systems (differential gear system) of automobiles employing conical roller bearings, it has been found that the axial clearance of the bearing becomes unduly large as a result of the above mentioned wear of the bearing so that the pressure preloading on the bearing is lost and thereby the maneuverability of the running car is reduced to a great extent while generating a harsh noise.
As a solution to this problem, it has been known to use a sealed bearing provided with a filter capable of filtering off the foreign matter or particles contained in the lubricating oil so as to prevent it from penetrating into the bearing. Such technique is disclosed Japanese Utility Model Publications No. 9307/1958 and No. 24167/1968. However, this known solution is not satisfactory and has the limitation that lubrication of the bearing is effected solely by lubricating oil which is contaminated with very fine foreign particles in the gear casing. The filter-ability of the filter provided in the bearing is not sufficient to filter out all foreign matter particles which may be extremely fine. Furthermore, there often may be insufficient lubrication of the bearing caused by filter clogging. For these reasons, the known solution has been found to be unsatisfactory to solve the problem of bearing wearing as described above. In this connection, it should be noted that all the known solutions to this problem are based upon the common knowledge in the art that the bearings used in power transmission gearing system be lubricated with oil reserved in the gear casing.